Stars

Sunspots, Flares, and Solar Wind

How fast does the solar wind travel?

When solar activity is particularly strong, such as during a solar flare, the stream of charged particles can increase dramatically. In that case, these ions can strike molecules in the upper atmosphere, causing them to glow. Those eerie, shimmering lights are called the aurora borealis (Northern Lights) and aurora australis (Southern Lights). During this time, Earth’s magnetic field can temporarily weaken, causing our atmosphere to expand; this can affect the motion of satellites in high-Earth orbit. In extremely strong periods of solar flux, electrical power grids can be affected.

The flow of plasma out from the Sun is generally continuous in all directions, typically moving at speeds of several hundred kilometers per second. It can, however, gust out of holes in the solar corona at 2.2 million miles per hour (one thousand kilometers per second) or faster. As the solar wind travels farther from the Sun, it picks up speed, but it also rapidly loses density.